/**
 * 权重随机
 */
module.exports = function (tasks, weightTotal) {
    let task;
    let weight = Math.ceil(Math.random() * weightTotal);
    
    for (let i = 0; i < tasks.length; i++) {
        weight -= tasks[i].weight || 0;
        if (weight <= 0) {
            task = tasks[i];
            break;
        }
    }
    
    return task || null;
};